An iterative algorithm for simulating heat recovery from exhaust gas – Application on generators
Résumé
This paper presents a parametric study that evaluates the heat that can be recovered from the gases resulting from the combustion of fuel in the power generators. This heat is evaluated by using a heat exchanger between the exhaust gases and another stream which is water. A geometrical configuration of the heat exchanger is considered and modeled; it considers that the water is flowing in the annulus while the gases are flowing through the inner tube in an opposite direction of a concentric tube type.
The appropriate thermal model and procedure are presented and applied to a 15 kVA power generator. Different cases are studied. In each case, the temperature of water leaving the heat exchanger is calculated for several water flow rates. It was shown that the temperature of water can reach 50.5 °C depending on the mass flow rate and the water inlet temperature. The corresponding recovered average heat rate is 4.3 kW. This recovered average heat rate increases to 7.7 kW when the mass flow rate of water increases from 0.05 kg/s to 0.5 kg/s.
Besides, the impact of the size of the power generator on the temperature of water leaving the heat exchanger and the recovered heat has been studied. Four different power generators are compared (15 kVA, 30 kVA, 60 kVA and 180 kVA). It was shown that, when the water inlet temperature and the water mass flow rate are equal to 10 °C and 0.4 kg/s, respectively, the temperature of water increases from 14.6 °C for a 15 kVA power generator to 39.4 °C for a 180 kVA power generator. The corresponding recovered average heat rate increases from 7.7 kW to 49.15 kW.